This invention relates to an extrusion type capillary rheometer for measuring the rheological properties, such as, flow property, viscosity and molecular weight distribution of materials such as plastics, ceramics and rubber. The invention also relates to a temperature measuring device for measuring the temperature of the sample bore of the rheometer.
Japanese Unexamined Utility Model Publication No. 59-101196 (Appln. No. 57-202566) discloses a rheometer of this type which comprises an electric furnace provided with a bore for a sample to be inserted into and a capillary connected to the lower end of the sample bore. The body of the furnace is sectioned into a plurality of zones, which are provided with individual heaters to heat the sample in the sample bore, and individual temperature sensors for detecting the temperatures of the respective furnace zones. One of the furnace zones is selected as a reference zone, and a controller controls the heater of the reference zone by a control signal so as to keep the zone at a predetermined temperature, and applies the control signal to the temperature controllers for the other furnace zones thereby to keep the temperature distribution of the whole furnace uniform. Then a plunger is inserted into the sample bore to extrude the heated sample out of the furnace through the capillary thereby to measure the rheological properties of the sample by the speed of movement of the plunger.
Japanese Unexamined Utility Model Publication No. 3-40550 (Appln. No. 1-101648) discloses a rheometer in which a separate barrel formed with a sample bore is disposed in the central portion of an electric furnace provided with heaters so as to make assemblage and maintenance of the furnace easy.
There are problems, however, to be solved in the known arrangements. Since there is a difference in temperature between the furnace zones and the inside of the sample bore, in the arrangement that the temperatures of the zones are merely controlled so as to coincide with the reference temperature, it is impossible to make the temperature distribution of the sample itself uniform because of thermal interference between the different furnace zones. In the arrangement that a separate barrel is disposed in the furnace, if the barrel is of a single body, a similar thermal interference occurs to prevent the temperature distribution in the sample from becoming uniform.